Ultrasound refers to a sound wave with a frequency greater than the upper limit of human hearing, which is generally over 20 kHz. In general, humans can hear sounds with a frequency between 20 Hz and 20 kHz.
Lake Ontario is one of the five Great Lakes of North America. It is bordered by the Canada and United States. It is the only Great Lake not to border the state of Michigan.
Nile is considered the Father of African Rivers. It is Stretching for approximately 6,695 km across 10 different countries, the Nile River is the longest river in the world.
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